This invention relates generally to a method and a system for printing on two sides of a media sheet, and more particularly, to the fusing temperature settings for an electrophotographic media handling system which first feeds a media sheet with a first side exposed to a print source, then feeds the media sheet with a second side exposed to the print source.
Printing to two sides of a media sheet, referred to as duplex printing, is a desirable feature in printing systems, especially in desktop or office color printers as printing speeds increase. The advantages of duplex printing include reducing the amount of paper required compared to one-sided (simplex) printing, and generating print sets with layouts resembling that of professionally printed books. Conventional duplex printing devices employ complex paper handling mechanisms. Typically, an extra tray is used for temporary storage of pages having printing on a first side. In an alternative approach a second paper path is provided to route a first printed page around the existing paper supply. Another approach utilizes a media re-feed guide that positively blocks the movement of media along a first path of travel and directs the media travel along a second path.
Similarly, duplex copying typically is accomplished by either one of two methods. In one method, first side copies are stacked in a duplex tray. When a set of first side copies is complete, the copies are fed out of the duplex tray and returned with an odd number of inversions along a duplex path to receive second side imaging. In an alternative method first side copies are returned directly to receive second side imaging without stacking.
The development of good quality color electrophotographic desktop printers has accelerated the acceptance of color printing and has spawned interest in being able to duplex print electrophotographic output. Because electrophotographic printing with toner requires fusing of the image to the final receiving substrate, duplex printing presents the problem of how to fuse the image on the second side of the final receiving substrate without melting and offsetting or lifting off the image on the first side of the substrate. Duplex printing with solid ink has a similar hurdle. Solid ink printing employs a wax-like ink base that is jetted at a molten temperature and then solidifies as it cools on intermediate and final receiving substrates. Printing on the second side of a media sheet without melting or destroying the hardened image on the first side has been a barrier to duplex printing. Paper curling has also been a problem.
Conventional approaches to achieve duplex printing have employed long paper paths, multiple imaging units, and many parts including additional temperature sensors and cooling devices. It is desirable to achieve a method and system for duplex printing in an electrophotographic desktop printer employing color toners in a single multi-color imaging unit. These problems are solved in the design of the present invention.